Re: What UPS to buy
On Sun, Feb 04, 2007 at 07:44:30PM -0500, Kevin Coyner wrote:
> On Sun, Feb 04, 2007 at 05:06:20PM -0700, Dave Thayer wrote......
> > On Sun, Feb 04, 2007 at 10:54:30PM +0000, J.A. de Vries wrote:
> > >
> One other consideration when buying a UPS ... if you plan to back up your
> battery powered UPS with a gas, propane or natural gas powered generator
> (because you expect power outages to last many hours if not days) then make
> sure the UPS you purchase supports an ability to set the voltage sensitivity.
>
> Your external generator usually takes a good 10 to 15 seconds before the
> transfer switch kicks in, making it essential to have a battery powered UPS.
> Once the external generator kicks in, the battery powered UPS should stand
> down. But the power from the external generator may not be steady, and you're
> battery powered UPS will trip in, and then trip out, repeatedly.
>
> Some of APC's UPS units allow you to set the voltage sensitivity via dip
> switches, some of the units allow you to set it via software, and some don't
> let you adjust the sensitivity. So if you plan to back up your battery
> powered UPS with an external generator, make sure to get a UPS with an
> adjustment for voltage sensitivity.
>
Or some can run in a dual-mode where unstable power is used to charge
the battery and the inverter is used to create clean power for the
computer. Some do this as an under-voltage protective measure. It
probably costs more.
Doug.
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